In fuel fired heating systems, it is usually necessary and desirable to provide a flue to conduct hot exhaust products from the heating appliance to be expelled through a chimney. However, when the fuel system is not fired, the flue may also act as a conduit for the flow of heated air from the environs, providing a ready escape for energy.
Applicant has identified the flue as a conduit for the loss of energy, and has discovered that if properly dampered off during the periods of time when the system is not actually fired, a savings in energy may be realized by inhibiting the conduction of heated air from the environs.
In some systems, such as an oil-fired heating appliance, spark ignition may be used when firing the unit and, therefore, there are no pilot systems to vent. However, in a gas-fired appliance, which often does not employ spark ignition but rather relies on a pilot flame for ignition, it is preferable to vent the pilot products of combustion through the flue. Therefore, as a means of venting the pilot products of combustion, and as a means of inducing a chimney effect in the flue to a degree, applicant has discovered that it is preferable not to completely obstruct the flue passageway, but rather to have predetermined clearance in the exhaust flow path which may be achieved by several ways. For example: clearance between the periphery of the damper plate and the wall of the flue, or by orifices through the closed damper plate.
It is therefore an object of the present invention to provide an energy-conserving flue damper which will control the exhaust flow of a flue between the on-off cycles of a fuel-fired heating system.
Another object of the present invention is to provide mutually exclusive circuits for the fuel supply system and the damper powering elements.
A still further object of the present invention is to provide predetermined clearances in the exhaust flow path of a dampered-off flue.